Bourdon tube having integral pointer

ABSTRACT

A Bourdon tube in which the integral free end is constructed to simulate a pointer. When employed in a pressure gauge, the freepointered end is moveable relative to a calibrated dial plate for indicating the values of pressure being sensed.

7 ii a 1 Umte States atet [151 3,641,820 Bissell Feb. 15, 1972 [54]BOURBON TUBE HAVING INTEGRAL 2,803,695 8/1957 PQINTER 2,224,841 12/19403,277,722 10/1966 [721 2,465,872 3/1949 Heath ..72/369 x [73] Assignee:Dresser Industries, Inc., Dallas, Tex.

- Primary ExaminerS. Clement Swisher [22] Ffled' Man AssistantExaminerDaniel M. Yasich PP- 17,681 Art0rney-Robert W. Mayer, Thomas P.Hubbard, Jr., Daniel Rubin, Raymond T. Majesko, Roy L. VanWinkle,William E. 521 US. Cl ..73/418, 29/422, 29/475 and Eddm [51] Int. Cl. 11 ..G0ll 7/04,.B23p 17/00 [58] field of Search ..73/418. 369; 72/369;113/54 A; l57| ABSTRACT 29/475 422 A Bourdon tube in which the integralfree end is constructed to simulate a pointer. When employed in apressure gauge, the [56] References cued free-pointered end is moveablerelative to a calibrated dial UNITED STATES PATENTS plate for indicatingthe values of pressure being sensed.

3,222,933 12/1965 Howard ..73/41 8 8 Claims, 9 Drawing Figures v I 0 I224 2O I I PATENTEUFEB 15 1972 FIG. 3(b) 27 FIG. 3(0) FIG. 3(0) INVENTORROBERT D. BISSELL ATTORNEY BOURDON TUBE HAVING INTEGRAL POINTERCROSS-REFERENCE TO RELATED APPLICATIONS None BACKGROUND OF THEINVENTION 1. The field of art to which the invention pertains includesthe art of measurement and testing as more specifically directed topressure gauges and their construction.

2. Pressure gauges enjoy very extensive commercial and industrial useand are consequently regarded as high production items. Because of suchwide use, they are supplied by a plurality of manufacturers and sold invery price conscious competition. Each manufacturer instinctivelystrives to reduce product costs by improvements, however marginal, whichreduce labor and/or materials that can contribute to cost savings in theend product. Dictating a minimum standard of quality is the need forprior marketing approval by the Underwriters Laboratory requiring thatthe gauge have a burst pressure rating at least five times the gaugerating.

Inherent in conventional-type pressure gauges is the Bourdon tube of apressuretight construction having a free end displaceably moveable inresponse to pressure changes. To translate tube movement into readoutpressure values it is customary to attach or otherwise connect a pointerto the free end and which then moves relative to a calibrated dialplate.

In relatively small pressure gauges on the order of one inch and less,the Bourdon tube is usually constructed as generally fiat in crosssection multiconvolution spiral to obtain the necessary operatinglineage in a minimum of consumed space. Specifically, such a Bourdontube when used with a nominal 1- inch gauge of actual 1 /16 diameterwill be approximately 7/16 inches in diameter of tubing generallyflattened to about 1/8 inches wide and 1/64 inches in depth. When ofthese small sizes, attaching a pointer to the free tube end has beenmost difficult frequently incurring an assembly cost disproportionate tothe overall cost of the instrument. In recognition of this problem oneapproach has been to attach a U-shaped member over the coil end and thetwo are then soldered together to produce the required pressuretightjoint thereat. While such a construction has worked well wheresufficiently large components are involved, it has been extremelydifficult heretofore to effect a pressuretight solder joint meeting U.L. specifications with Bourdon tube constructions of dimensions on theorder given above. Likewise, attempts to previously produce integralpointer constructions have proved unsuccessful because of an inabilityto assuredly produce the required pressuretight closing ofthe tube endthereat.

SUMMARY OF THE INVENTION The invention relates to the method of forminga simulated pointer integrally constructed at the free end of a Bourdontube and the product thereof. More specifically, the invention relatesto Bourdon tube construction in which attachments or connections of aseparate pointer member to provide readout indications as in the priorart is eliminated. By forming a pointer in accordance herewith,difficulties associated with pointer construction in the prior art areovercome while at the same time assuredly and reliably producing therequired pressuretight tube closing thereat on a high volume, productionbasis.

It is therefore an object of the invention to provide a novel method forforming a pointer at the free end of a Bourdon tube.

It is a further object of the invention to provide a method as in thepreviously recited object which lends itself to production manufactureof small size tube coils to overcome the difficulties associated withprior art construction.

It is a further object of the invention to provide a method of Bourdontube pointer construction affording substantial costs savings overmethods previously employed and without sacrifice in the reliability oreffectiveness of the other active tube properties.

It is a still further object of the invention to provide a Bourdon tubepointer construction produced by the methods of the aforementionedobjects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is side elevation partially insection of a typical pressure gauge constructed with a Bourdon tube inaccordance herewith;

FIG. 2 is a front view of the Bourdon tube in accordance herewith asrepresented by a section taken substantially along the lines 22 of FIG.1;

FIG. 3 (a), (b), (c) are plan, side, and end views respectively of thefirst step in pointer formation;

FIG. 4 (a), (b), (c) are the plan, side, and end views respectively ofthe second step in pointer formation; and

FIG. 5 diagrammatically illustrates the final step in pointer formation.

With reference to FIGS. 1 and 2 there is shown a pressure gaugedesignated 10 of a conventional type including a Bourdon tube 11constructed in accordance herewith. The gauge typically consists of acase 12 closed at its front by a transparent crystal l3 and at the rearcontains a socket member 16 having a threaded end 17 for mounting thegauge in a suitably provided connector. Centrally within the socket isan open bore 18 in which the fixed open end 19 of the Bourdon tube issecured. As can be seen, the Bourdon coil is of a spiralmulticonvolution construction axially supported slightly forward of adial plate 20 having pressure scale graduations 21 within the operatingrange of the instrument. By this arrangement, a simulated pointer 24 atthe free end of tube '11 will move relative to the dial graduations forindicating pressure variations to which the Bourdon tube is caused torespond. A centrally circular opaque area 22 can be provided on crystal13 when desired so as to conceal the Bourdon coil directly behind.

Formation of the pointer in accordance herewith will now be describedwith reference to FIGS. 3-5. As can be appreciated, the steps of pointerformation can either precede or succeed forming the active portion ofthe Bourdon tube. Preferably the pointer is formed simultaneously withtube flattening prior to coiling. In either event forming the pointer isbegun with a short radial end section designated 25 ultimately bentoutward approximately to the plane of the last spiral convolution.Following the latter, a tipmost or terminal end section 26 is bent flatto a plane centrally located and extending transverse with respect tothe remaining integrally connected portion of section 25. Thereaftereach of the corners 27 and 28, as defined by the dashed lines in FIG. 3(a), are folded or bent downward from a center location at the terminaledge. Bending is continued until reaching the relationship of FIG. 4 inwhich the folds terminate at a spacing 30 between them defined byopposite parallel and juxtaposed comer ends 31 and 32. The pointerconfiguration thus formed is then metallurgically sealed by beingmomentarily dipped into a pot of molten solder 35 (FIG. 5) to close offall openings against pressure leakage. At the same time the solderprovides a bond between ends 31 and 32 of sufi'icient mechanicalstrength to resist distortion from subsequently imposed internalpressures. The last soldering step completes the integral pointerformation and by view of the simplicity of procedures it can beappreciated that the entire integral pointer construction can becompleted on a production basis in approximately six seconds.

By the above description there is disclosed a novel Bourdon tubeconstruction having a simulated pointer formed integrally part of themoveable end. The tube when so constructed has a burst pressure ratingexceeding U. L. specifications and is mounted into a conventional-typepressure gauge wherein the pointer is situated to be displaced oppositea calibrated dial indicating pressure values received within the tube.The method of construction can be achieved at minimum cost and when theend product is viewed through the crystal the simulated pointer appearsas a conventional type pointer as in the prior art. At the same time theformer problems associated with attaching or connecting pointers of theprior art are overcome in a manner contributing substantially to amanufacturing cost reduction of particularly small gauge diameters. Sucha result has not been previously known despite the simplicity inherentin the method by which the pointer construction hereof is obtained.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specification shall be interpreted asillustrative and not in a limiting sense.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A method of forming an integral simulated pointer at the moveable endof a Bourdon tube, comprising the steps of:

a. bending a terminal end section of a Bourdon tube to a substantiallyflattened plane extending generally transverse to the integrallyconnecting portion of said tube; folding the corners of said flattenedsection from a central location at the terminal edge thereof until thecomers are spaced apart juxtaposed and substantially parallel to eachother; and connecting said juxtaposed corner edges into apressureresistant joint thereat.

2. A method according to claim 1 in which the step of connecting saidcorner edges comprises applying a solder bond thereat.

3. A method according to claim 1 in which said bending step compriseseffecting opposed bidirectional bending forming a flattened planegenerally centrally located with respect to the connecting integralportion of said tube.

4. A method according to claim 1 in which the said step of connectingsaid corner edges comprises applying a metallurgical bond thereat.

S. In a Bourdon tube including an open end in which to receive pressureto be sensed and an opposite end moveable in response to pressurechanges received at said open end, the improvement comprising:

a simulated pointer at the terminal portion of said moveable endcomprising an integral part of said moveable end bent to simulate apointer when viewed in a direction generally toward the coiled axis ofsaid tube, said simulated pointer including:

a. a substantially flat face surface extending generally transverse tothe plane of the integrally connected tube portion thereat;

b. the apexmost end of said simulated pointer being represented byoppositely bent corners originating from the terminal edge of saidpointer face surface; and

c. said bent corners terminating spaced apart extending juxtaposedgenerally parallel to each other and secured in a pressure-resistantjoint.

6. in a Bourdon tube according to claim 5 further including thecombination of a dial plate and a casing cooperating with said Bourdontube to form an indicating pressure gauge.

7. in the improvement according to claim 5 in which saidpressure-resistant joint comprises a metallurgical bond.

8. 1n the improvement according to claim 7 in said pressureresistantjoint comprises a solder connection.

1. A method of forming an integral simulated pointer at the moveable endof a Bourdon tube, comprising the steps of: a. bending a terminal endsection of a Bourdon tube to a substantially flattened plane extendinggenerally transverse to the integrally connecting portion of said tube;b. folding the corners of said flattened section from a central locationat the terminal edge thereof until the corners are spaced apartjuxtaposed and substantially parallel to each other; and c. connectingsaid juxtaposed corner edges into a pressureresistant joint thereat. 2.A method according to claim 1 in which the step of connecting saidcorner edges comprises applying a solder bond thereat.
 3. A methodaccording to claim 1 in which said bending step comprises effectingopposed bidirectional bending forming a flattened plane generallycentrally located with respect to the connecting integral portion ofsaid tube.
 4. A method according to claim 1 in which the said step ofconnecting said corner edges comprises applying a metallurgical bondthereat.
 5. In a Bourdon tube including an open end in which to receivepressure to be sensed and an opposite end moveable in response topressure changes received at said open end, the improvement comprising:a simulated pointer at the terminal portion of said moveable endcomprising an integral part of said moveable end bent to simulate apointer when viewed in a direction generally toward the coiled axis ofsaid tube, said simulated pointer including: a. a substantially flatface surface extending generally transverse to the plane of theintegrally connected tube portion thereat; b. the apexmost end of saidsimulated pointer being represented by oppositely bent cornersoriginating from the terminal edge of said pointer face surface; and c.said bent corners terminating spaced apart extending juxtaposedgenerally parallel to each other and secured in a pressure-resistantjoint.
 6. In a Bourdon tube according to claim 5 further including thecombination of a dial plate and a casing cooperating with said Bourdontube to form an indicating pressUre gauge.
 7. In the improvementaccording to claim 5 in which said pressure-resistant joint comprises ametallurgical bond.
 8. In the improvement according to claim 7 in saidpressure-resistant joint comprises a solder connection.